1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device. More particularly, the present invention relates to a vertical alignment (VA) mode liquid crystal display device.
2. Discussion of the Related Art
The liquid crystal molecules for a LCD device have orientation characteristics of arrangement resulting from their thin and long shape. An arrangement direction of the liquid crystal molecules can be controlled by applying an electrical field to them. Thus, the LCD device displays images using a variation of transmittance of the liquid crystal molecules by controlling magnitudes of the electric field. The LCD device includes a thin film transistor (TFT) as a switching element, referred to as an active matrix LCD (AM-LCD) device, and has excellent characteristics of high resolution and displaying moving images.
A related art LCD device includes a first substrate, a second substrate and a liquid crystal layer. The first substrate includes a pixel electrode, and the second substrate includes a color filter layer and a common electrode. The first and second substrates face each other, and the liquid crystal layer is interposed therebetween. The related art LCD device displays images using a vertical electric field between the pixel and common electrodes. The LCD device using the vertical electric field has a high transmittance and a high aperture ratio. However, the LCD device has problems such as narrow viewing angle, and low contrast ratio.
To resolve the above-mentioned problems, the VA mode LCD device having a wide viewing angle is suggested.
FIG. 1 is a cross-sectional view of a VA mode LCD device according to the related art. As shown in FIG. 1, the VA mode LCD device includes first and second substrates 10 and 20 and the liquid crystal layer 30 therebetween. The pixel and common electrodes 12 and 24 are formed on the first and second substrates 10 and 20, respectively. The pixel and common electrodes 12 and 24 include a pixel electrode rib 12a and a common electrode rib 24a, respectively. When different voltages are applied to the pixel and common electrodes 12 and 24, the electric field 50 between the pixel and common electrodes 12 and 24 is distorted by the pixel electrode rib 12a and the common electrode rib 24a such that first and second oblique electric field 50a and 50b are induced. Thus, the liquid crystal layer 30 has two domains such that the viewing angle is improved and the VA mode LCD device has a wide viewing angle.
One of the pixel electrode ribs 12a and the common electrode ribs 24a may be omitted. Moreover, the pixel electrode 12 and the common electrode 24 may have a slit instead of the pixel electrode rib 12a and the common electrode rib 24a. 
The related art LCD device includes a backlight assembly on an outer surface of the second substrate as a light source. The LCD device including the backlight assembly may be referred to as a transmissive type LCD device. Displayed images have light between 3% and 8% of original light emitted from the backlight assembly in the transmissive type LCD device. Accordingly, to display images of high luminance, there is a problem of power consumption in the backlight assembly.
To resolve the problem in the transmissive type LCD device, a reflective type LCD device, which does not include the backlight assembly as the light source, is suggested. The reflective type LCD device includes a reflective electrode instead of the pixel electrode. The pixel electrode has a transparent property in the transmissive type LCD device, but the reflective electrode has a reflective property in the reflective type LCD device. The reflective electrode reflects outside light or artificial light. Unfortunately, there may be circumstances in which the outside light and the artificial light may not exist such that the reflective type LCD device does not display images in the dark.
To resolve these problems of the transmissive type LCD device and the reflective type LCD device, a transflective type LCD device having advantages of the transmissive type LCD device and the reflective type LCD device is suggested. The transflective type LCD device includes a transmissive area and a reflective area in the pixel region to convert between the transmissive mode and the reflective mode depending on the surroundings.
Moreover, to improve the viewing angle of the transflective type LCD device, the VA mode LCD device is incorporated into the transflective type LCD device. It may be referred to as a transflective VA mode LCD device. Since the transflective VA mode LCD device uses outside light, luminance of the images may be decrease. Moreover, when the transflective VA mode LCD device has multiple domains to improve the viewing angle, luminance further decreases because of area occupied by a disclination between domains.